Geologic formations are used for many applications such as hydrocarbon production, geothermal production, and carbon dioxide sequestration. Typically, boreholes are drilled into the formations to provide access to them. Drilling rigs disposed at the surface, whether it is land or water, operate drillstrings that are connected to drill bits for drilling the boreholes. In that it is very expensive to operate a drilling rig, efficiencies can be achieved by precisely drilling a borehole to achieve a desired geometry and end location. When boring in an earth formation, a predetermined drill path extending into the earth formation may be provided for an operator to follow. The drill path may curve, turn, or otherwise be nonlinear, requiring the operator to control a direction in which an earth-boring tool proceeds into the earth formation. Components for inclusion in a drillstring, such as a bottomhole assembly (BHA) and one or more earth-boring tools (e.g., an earth-boring drill bit, a reamer, or another tool configured to remove earth material when forming or enlarging a borehole), may be selected for their ability to perform within, and to create, a nonlinear borehole.
The processes of directional drilling are complicated by the complex interaction of forces between the drill bit and the walls of the subterranean formation lining the well borehole. In drilling with rotary drill bits and, particularly with fixed-cutter type rotary drill bits, it is known that if a lateral force (often referred to as a side force or a radial force) is applied to the drill bit, the drill bit may “walk” or “drift” from the straight path that is parallel to the intended longitudinal axis of the well borehole. When a drill bit walks in such a way that the direction angle increases, the drill bit may be said to walk to the right or to exhibit “right walk.” Similarly, when a drill bit walks in such a way that the direction angle decreases, the drill bit may be said to walk to the left or to exhibit “left walk.” When a drill bit does not walk or drift away from the straight path that is parallel to the longitudinal axis of the well borehole at the bottom thereof, the bit may be referred to as an “anti-walk” drill bit and may be said to exhibit “neutral walk.” In a similar manner, when a drill bit drifts in a direction such that the inclination angle increases, the drill bit is said to exhibit a tendency to “build,” and when a drill bit drifts in a direction such that the inclination angle decreases, the drill bit is said to exhibit a tendency to “drop.”
Many factors or variables may at least partially contribute to the reactive forces and torques applied to a drill bit and BHA by the surrounding subterranean formation. Such factors and variables may include, for example, the “weight-on-bit” (WOB), the rotational speed of the bit and BHA, the physical properties and characteristics of the subterranean formation being drilled, the hydrodynamics of the drilling fluid, the length and configuration of the BHA to which the bit is mounted, and various design factors of the drill bit and BHA including the cutting element size, radial placement, back (or forward) rake, side rake, etc. Various complex modeling and computational methods known in the art may be used to calculate the forces and torques acting on a drill bit and BHA under predetermined conditions and parameters. For example, a wellbore design may be created using three-dimensional modeling software by inputting design variables associated with drilling parameters and lithology data and using the computational software to estimate by mathematical calculations the reactive forces and torques applied to the drill bit and BHA by the surrounding subterranean formation during drilling to estimate the trajectory of the drill bit and BHA through the subterranean formation.